Use of water soluble polymers as dispersion agent of aqueous calcium carbonate suspension, resulting aqueous suspensions and their uses

ABSTRACT

The invention relates to the use of homopolymers and/or water-soluble copolymers of acrylic acid with one or more acrylic, vinyl or allylic monomers as dispersing agents for aqueous suspensions of mineral particles issuing from a mechanical and/or thermal reconcentration step following upon a step of wet grinding without the use of a dispersant and at low concentration in terms of dry matter. 
     The invention also relates to the said aqueous suspensions and their uses in the fields of paper, paint, fillers for synthetic resins and rubbers, detergent and cleaning formulations, ceramics, drilling fluids, cements, plasters and other fields of application in civil engineering and the construction industry.

The invention relates to the use of homopolymers and/or water-solublecopolymers of acrylic acid with one or more acrylic, vinyl or allylicmonomers as dispersing agents for aqueous suspensions of calciumcarbonate.

The invention also relates to the said aqueous suspensions of calciumcarbonate and their uses in the fields of paper, like notably themanufacture or coating of paper, those of paint, fillers for syntheticresins and rubbers, detergent and cleaning formulations, and any otherfield using said suspensions such as notably ceramics, drilling fluids,cements, plasters and other fields of application in civil engineeringand the construction industry.

For a long time already, persons skilled in the art have known about theuse of grinding and/or dispersing agents for aqueous suspensions ofmineral particles constituted by acrylic polymers and/or copolymers, oflow molecular weight, totally or partially neutralized by variousneutralizing agents (FR 2 603 042, EP 0 100 947, EP 0 127 388, EP 0 129329 and EP 0 542 644).

Persons skilled in the art also know about the use of grinding and/ordispersing agents constituted by the fraction of acrylic polymers and/orcopolymers whose specific viscosity is between 0.3 and 0.8 (patents FR 2488 814, EP 0 100 948 and EP 0 542 643).

But these various types of grinding and/or dispersing agents of lowmolecular weight which make it possible to obtain aqueous suspensions ofmineral particles refined and stable over time do not allow the puttingback into suspension or redispersal in water of mineral particles, suchas notably calcium carbonate, issuing from a mechanical and/or thermalreconcentration step following upon a step of wet grinding without theuse of a dispersant and at low concentration in terms of dry matter.Such mineral particles, issuing from this mechanical and/or thermalreconcentration step following upon a step of wet grinding without theuse of a dispersant, pose serious usage problems for persons skilled inthe art who must disperse these mineral particles in the form ofsuspensions at very high concentration in terms of dry matter in orderto be able to offer them to the user in a form which can be manipulatedby said user.

Confronted with this problem, the Applicant then found, surprisingly,that the selection of homopolymers of acrylic acid and/or water-solublecopolymers of acrylic acid with one or more acrylic, vinyl or allylicmonomers of a different and higher molecular weight than all theliterature known to date teaches (and notably the patent application EP0 850 685), makes it possible to put into aqueous suspension the mineralparticles issuing from this mechanical and/or thermal reconcentrationstep following upon a step of wet grinding without the use of adispersant and at low concentration in terms of dry matter.

By a step of wet grinding without the use of a dispersant, the applicantmeans a step of wet grinding without any dispersant but possibly withsmall quantities of flocculating agent up to 500 ppm.

Thus, one of the aims of the invention is the use of homopolymers ofacrylic acid and/or water-soluble copolymers of acrylic acid with one ormore acrylic, vinyl or allylic monomers of a molecular weightcorresponding to a viscosity index with a value from 0.08 to 0.80, andpreferentially from 0.20 to 0.60, as dispersing agents for aqueoussuspensions of mineral particles issuing from a mechanical and/orthermal reconcentration step following upon a step of wet grindingwithout the use of a dispersant and at low concentration in terms of drymatter.

Similarly, another aim of the invention is to provide a dispersing agentfor aqueous suspensions of mineral particles issuing from a mechanicaland/or thermal reconcentration step following upon a step of wetgrinding without the use of a dispersant and at low concentration interms of dry matter.

An additional aim of the invention is to provide a method of puttingsaid mineral particles into aqueous suspension using the selection ofhomopolymers of acrylic acid and/or water-soluble copolymers of acrylicacid with one or more acrylic, vinyl or allylic monomers of a molecularweight corresponding to a viscosity index with a value from 0.08 to0.80, and preferentially from 0.20 to 0.60.

Another aim of the invention, besides those already mentioned, is toprovide aqueous suspensions of refined mineral materials obtained by theaforementioned method, and characterised in that they contain from 0.1%to 2% by dry weight, and preferentially from 0.3% to 1.0% by dry weight,with respect to the dry weight of mineral material, of aqueoussuspension dispersing agent according to the invention.

Finally, an additional aim of the invention concerns the use of thesemineral aqueous suspensions in the fields of mass filling and coating ofpaper as well as those of paint, ceramics, drilling fluids, fillers forsynthetic resins and rubbers, detergent and cleaning formulations, andany other field using said suspensions such as notably cements, plastersand other fields of application in civil engineering and theconstruction industry.

These aims are achieved by virtue of the use according to the inventionof homopolymers of acrylic acid and/or water-soluble copolymers ofacrylic acid with one or more acrylic, vinyl or allylic monomers of amolecular weight corresponding to a viscosity index with a value from0.08 to 0.80, and preferentially from 0.20 to 0.60.

These homopolymers and/or copolymers result from the various knownmethods of radical polymerization using the polymerization initiatorswell known to persons skilled in the art such as, for example,hydroxylamine-based compounds or also using the polymerizationinitiators such as peroxides like notably hydrogen peroxide, tert-butylhydroperoxide or the persalts like notably sodium persulphate, ammoniumpersulphate, potassium persulphate or analogues, or also sodiumhypophosphite, hypophosphorous acid or again also phosphorous acidand/or their salts in the possible presence of metallic salts forexample of iron or copper in a polymerization medium which can be water,methanol, ethanol, propanol, isopropanol, butanols, or their mixtures oralso dimethylformamide, dimethylsulphoxide, tetrahydrofurane, acetone,methyl ethyl ketone, ethyl acetate, butyl acetate, hexane, heptane,benzene, toluene, xylene, and possibly in the presence of molecular masscontrollers also referred to as chain transfer agents such as notablymercaptoethanol, thioglycolic acid and its esters, n-dodecyl mercaptan,acetic, tartaric, lactic, citric, gluconic or glucoheptonic acids,2-mercaptopropionic acid, thiodiethanol, halogenated solvents likecarbon tetrachloride, chloroform, methylene chloride, the ethers ofmonopropylene glycol, or their mixtures and analogues.

These homopolymers and/or copolymers used as dispersing agents accordingto the invention result from the various aforementioned methods ofradical polymerization of one at least of the monomers chosen from amongacrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaricacid, isocrotonic, aconitic, mesaconic, sinapic, undecylenic, angelic orcanellic acid, and/or acrylamido methyl propane sulphonic acid in acidor partially neutralized form, or also from among acrylamide,methacrylamide, the esters of acrylic or methacrylic acids such asnotably ethyl acrylate, butyl acrylate, methyl methacrylate, phosphateof acrylate or methacrylate of ethylene or propylene glycol or alsoagain from among vinylpyrrolidone, vinylcaprolactame, isobutylene,diisobutylene, vinyl acetate, styrene, alphamethylstyrene, styrenesodium sulphonate vinylmethylether, or the allylics such as notablyallylamine and its derivatives.

These homopolymers and/or copolymers used as dispersing agents accordingto the invention are partially or totally neutralized by one or moreneutralizing agents having a monovalent function and possibly apolyvalent function.

The neutralizing agents having a monovalent function are chosen from thegroup constituted by the compounds containing alkaline cations, inparticular sodium and potassium, or also lithium, ammonium, or again thealiphatic and/or cyclic primary or secondary amines such as for examplethe ethanolamines, mono and diethylamine or also cyclohexylamine.

The neutralizing agents having a polyvalent function are chosen from thegroup constituted by the compounds containing alkaline-earth divalentcations, in particular magnesium and calcium, or also zinc, and likewiseby the trivalent cations, including in particular aluminium, or also bycertain compounds containing higher-valency cations.

The homopolymers and/or copolymers designed to be used according to theinvention as dispersing agents in water for mineral particles issuingfrom a mechanical and/or thermal reconcentration step following upon astep of wet grinding without the use of a dispersant and at lowconcentration in terms of dry matter are selected from among thehomopolymers or copolymers having a molecular weight corresponding to aviscosity index with a value from 0.08 to 0.80, and preferentially from0.20 to 0.60.

The molecular weight of the homopolymers or copolymers is measured onthe form of the polymer salified with soda and according to theprocedure described below and will be referred to as the viscosity indexthroughout the remainder of the present application.

To do this, the acid form of the compound whose viscosity index it isnecessary to determine is 100% neutralized with soda and then diluted at50 g/l in bipermutated water. This parent solution, which then has aconcentration denoted c₀, is subjected to the following dilutions:(2/3)c₀, (1/2)c₀, (1/3)c₀, (1/4)c₀, (1/6)c₀, (1/12)c₀, (1/18)c₀,(1/24)c₀, (1/36)c₀.

The specific viscosity for each solution is then determined by means ofa Schott AVS/500 viscometer equipped with an Ubbelohde tube of reference53010/I and constant 0.01 and the specific viscosity curve is plotted asa function of the concentration.

The linear part of the curve makes it possible to obtain the viscosityindex according to the equation

Viscosity index=Limit of the specific viscosity when the concentrationtends to zero.

The refined mineral substances to be put into suspension according tothe invention are chosen from among the synthetic calcium carbonates orthe natural calcium carbonates such as notably chalk, calcite, marble oralso dolomite or their mixtures.

Thus, the use according to the invention of a selection of homopolymersof acrylic acid and/or water-soluble copolymers of acrylic acid with oneor more acrylic, vinyl or allylic monomers and the development of adispersing agent according to the invention permits the putting intosuspension of mineral substances issuing from a mechanical and/orthermal reconcentration step following upon a step of wet grindingwithout the use of a dispersant and at low concentration in terms of drymatter and thus allows the obtaining of aqueous suspensions of refinedmineral materials obtained by the aforementioned method and containingsaid dispersing agent according to the invention.

In practice, the operation of dispersing or putting into aqueoussuspension of said mineral substances consists of adding, underagitation, the necessary amount of dispersing agent according to theinvention so as to obtain an aqueous suspension of said mineralmaterials, issuing from a mechanical and/or thermal reconcentrationstep, having a concentration in terms of dry matter of at least 60% witha Brookfield viscosity strictly less than 2000 mPa.s measured at 100 rpmimmediately after the putting into suspension and a Brookfield viscositystrictly less than 20,000 mPa.s, measured at 10 rpm after eight days'storage without agitation, that is to say so as to obtain an aqueoussuspension of said mineral materials highly concentrated in terms of drymatter which remains able to be manipulated by the user even after astorage of a number of days and without agitation.

The scope and advantage of the invention will be better understood byvirtue of the following examples, which are not restrictive in anyrespect.

EXAMPLE 1

This example relates to the selection of the molecular weight (expressedby the viscosity index) of the dispersing agent allowing the puttinginto aqueous suspension of natural calcium carbonate ground with nodispersant at a granulometry of which 73% of the particles have adiameter less than one micrometer determined by the Micromeriticscompany Sedigraph 5100 measurement and issuing from a mechanicalreconcentration of the centrifugation type following upon this wetgrinding at low concentration in terms of dry matter and with nodispersant.

This natural calcium carbonate is a marble.

For each test, the aqueous suspension of marble was prepared byintroduction, into the filter cake issuing from the centrifugation, of0.4% by dry weight of dispersing agent to be tested with respect to thedry weight of said filter cake to be put into suspension so as to obtainan aqueous suspension of calcium carbonate at a concentration in termsof dry matter equal to 61%.

After twenty minutes' agitation, a sample of the calcium carbonatesuspension obtained is retrieved in a flask and its Brookfield viscosityis measured by means of an RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 100 rpm with theappropriate spindle.

After a time of 8 days in the flask, the Brookfield viscosity of thesuspension is measured by introduction, into the non-agitated flask, ofthe appropriate spindle of the RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 10 rpm (PRE-AGviscosity=Brookfield viscosity before agitation).

The different homopolymers tested are:

Test 1

This test, which illustrates the prior art, uses a totally neutralizedsodium polyacrylate with viscosity index equal to 0.04 measuredaccording to the aforementioned procedure.

Test 2

This test, which illustrates the prior art, uses a mixed polyacrylate ofmagnesium and sodium (50% magnesium-50% sodium by mole) whose salifiedwith soda form has a viscosity index equal to 0.04 measured according tothe aforementioned procedure.

Test 3

This test, which illustrates the prior art, uses a totally neutralizedsodium polyacrylate with viscosity index equal to 0.07 measuredaccording to the aforementioned procedure.

Test 4

This test, which illustrates the invention, uses a totally neutralizedsodium polyacrylate with viscosity index equal to 0.10 measuredaccording to the aforementioned procedure.

Test 5

This test, which illustrates the invention, uses a totally neutralizedsodium polyacrylate with viscosity index equal to 0.31 measuredaccording to the aforementioned procedure.

Test 6

This test, which illustrates the invention, uses a totally neutralizedsodium polyacrylate with viscosity index equal to 0.39 measuredaccording to the aforementioned procedure.

Test 7

This test, which illustrates the invention, uses a totally neutralizedsodium polyacrylate with viscosity index equal to 0.44 measuredaccording to the aforementioned procedure.

Test 8

This test, which illustrates the invention, uses a totally neutralizedsodium polyacrylate with viscosity index equal to 0.75 measuredaccording to the aforementioned procedure.

Test 9

This test, which illustrates a field outside the invention, uses atotally neutralized sodium polyacrylate with viscosity index equal to0.83 measured according to the aforementioned procedure.

All the experimental results are recorded in the following Table 1.

TABLE 1 Brookfield viscosity Brookfield viscosity Viscosity CompositionDose T = 0 T = 8D PRE-AG Tests index (%) (%) 100 rpm (mPa · s) 10 rpm(mPa · s) 1 Prior art 0.04 AA 100 0.4 6000 34000 2 Prior art 0.04 AA 1000.4 3500 32000 3 Prior art 0.07 AA 100 0.4 2600 27000 4 Invention 0.10AA 100 0.4 1800 19000 5 Invention 0.31 AA 100 0.4 880 9000 6 Invention0.39 AA 100 0.4 280 6000 7 Invention 0.44 AA 100 0.4 320 7000 8Invention 0.75 AA 100 0.4 350 12000 9 Outside the 0.83 AA 100 0.4 44021000 invention AA: Acrylic acid T = 0 means initial Brookfieldviscosity of the suspension T = 8D PRE-AG means Brookfield viscosityafter 8 days' storage without agitation

The reading of Table 1 allows it to be noted that, contrary to anyexpectation of persons skilled in the art, the homopolymers of acrylicacid having a viscosity index selected from the interval between 0.08and 0.80 make it possible to put into suspension a calcium carbonateissuing from a mechanical reconcentration of the centrifugation typefollowing upon a wet grinding at low concentration in terms of drymatter and with no dispersant.

EXAMPLE 2

This example relates to the use of copolymers according to the inventionas dispersing agents allowing the putting into aqueous suspension ofnatural calcium carbonate ground with no dispersant at a granulometry ofwhich 73% of the particles have a diameter less than one micrometerdetermined by the Micromeritics company Sedigraph 5100 measurement andissuing from a mechanical reconcentration of the centrifugation typefollowing upon this wet grinding at low concentration in terms of drymatter and with no dispersant.

This natural calcium carbonate is a marble.

The dispersing agents of the different tests of the example are testedwith the same equipment and the same operating method as in the previousexample.

Test 10

This test, which illustrates a field outside the invention, uses acopolymer, 100% neutralized with soda, with viscosity index equal to0.05 measured according to the aforementioned procedure and composed, interms of weight percentage, of 70% acrylic acid and 30% methacrylicacid.

Test 11

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.12 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% methacrylic acid.

Test 12

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.73 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% methacrylic acid.

Test 13

This test, which illustrates a field outside the invention, uses acopolymer, 100% neutralized with soda, with viscosity index equal to0.06 measured according to the aforementioned procedure and composed, interms of weight percentage, of 80% acrylic acid and 20% ethylene glycolmethacrylate phosphate.

Test 14

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.08 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 80% acrylic acid and 20% ethylene glycolmethacrylate phosphate.

Test 15

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.11 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 80% acrylic acid and 20% ethylene glycolmethacrylate phosphate.

Test 16

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.17 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 80% acrylic acid and 20% ethylene glycolmethacrylate phosphate.

Test 17

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.26 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 80% acrylic acid and 20% ethylene glycolmethacrylate phosphate.

Test 18

This test, which illustrates a field outside the invention, uses acopolymer, 100% neutralized with soda, with viscosity index equal to0.81 measured according to the aforementioned procedure and composed, interms of weight percentage, of 80% acrylic acid and 20% ethylene glycolmethacrylate phosphate.

Test 19

This test, which illustrates a field outside the invention, uses acopolymer, 100% neutralized with soda, with viscosity index equal to0.06 measured according to the aforementioned procedure and composed, interms of weight percentage, of 70% acrylic acid and 30% acrylamidomethyl propane sulphonic acid.

Test 20

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.10 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% acrylamido methyl propanesulphonic acid.

Test 21

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.14 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% acrylamido methyl propanesulphonic acid.

Test 22

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.35 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% acrylamido methyl propanesulphonic acid.

Test 23

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.48 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% acrylamido methyl propanesulphonic acid.

Test 24

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.54 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% acrylamido methyl propanesulphonic acid.

Test 25

This test, which illustrates a field outside the invention, uses acopolymer, 100% neutralized with soda, with viscosity index equal to0.07 measured according to the aforementioned procedure and composed, interms of weight percentage, of 30% acrylic acid and 70% acrylamide.

Test 26

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.15 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 30% acrylic acid and 70% acrylamide.

Test 27

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.43 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 30% acrylic acid and 70% acrylamide.

Test 28

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.56 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 30% acrylic acid and 70% acrylamide.

Test 29

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.67 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 30% acrylic acid and 70% acrylamide.

Test 30

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.33 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% methacrylamide.

Test 31

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.28 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% styrene sodiumsulphonate.

Test 32

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.48 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 80% acrylic acid and 20% vinylpyrrolidone.

All the experimental results are recorded in the following Table 2.

TABLE 2 Brookfield viscosity Brookfield viscosity Viscosity CompositionDose T = 0 T = 8D PRE-AG Tests index (%) (%) 100 rpm (mPa · s) 10 rpm(mPa · s) 10 Outside the invention 0.05 AA 70 MAA 30 0.4 2300 19000 11Invention 0.12 AA 70 MAA 30 0.4 1260 15000 12 Invention 0.73 AA 70 MAA30 0.4 600 9000 13 Outside the invention 0.06 AA 80 EGMAPO₄ 20 0.4 120022000 14 Invention 0.08 AA 80 EGMAPO₄ 20 0.4 730 8000 15 Invention 0.11AA 80 EGMAPO₄ 20 0.4 600 7000 16 Invention 0.17 AA 80 EGMAPO₄ 20 0.4 4209000 17 Invention 0.26 AA 80 EGMAPO₄ 20 0.4 450 8000 18 Outside theinvention 0.81 AA 80 EGMAPO₄ 20 0.4 550 33000 19 Outside the invention0.06 AA 70 AMPS 30 0.4 1150 22000 20 Invention 0.10 AA 70 AMPS 30 0.4850 9000 21 Invention 0.14 AA 70 AMPS 30 0.4 670 9000 22 Invention 0.35AA 70 AMPS 30 0.4 540 5000 23 Invention 0.48 AA 70 AMPS 30 0.4 520 1000024 Invention 0.54 AA 70 AMPS 30 0.4 700 16000 25 Outside the invention0.07 AAM 70 AA 30 0.4 Dispersion impossible 26 Invention 0.15 AAM 70 AA30 0.4 1440 11000 27 Invention 0.43 AAM 70 AA 30 0.4 868 10450 28Invention 0.56 AAM 70 AA 30 0.4 780 10000 29 Invention 0.67 AAM 70 AA 300.4 800 12000 30 Invention 0.33 AA 70 MAAM 30 0.4 550 11000 31 Invention0.28 AA 70 SSNa 30 0.4 700 10500 32 Invention 0.48 AA 80 VP 20 0.4 90011000 AA: Acrylic acid AAM: Acrylamide MAA: Methacrylic acid AMPS:2-acrylamido-2-methyl propane sulphonic acid EGMAPO₄: Ethylene glycolmethacrylate phosphate MAAM: Methacrylamide SSNa: Styrene sodiumsulphonate VP: Vinylpyrrolidone T = 0 means initial Brookfield viscosityof the suspension T = 8D PRE-AG means Brookfield viscosity after 8 days'storage without agitation

The reading of Table 2 allows it to be noted that the copolymers ofacrylic acid having a viscosity index selected from the interval between0.08 and 0.80 make it possible to put into suspension a calciumcarbonate issuing from a mechanical reconcentration of thecentrifugation type following upon a wet grinding at low concentrationin terms of dry matter and with no dispersant.

EXAMPLE 3

This example relates to the use of copolymers according to the inventionas dispersing agents allowing the putting into aqueous suspension ofnatural calcium carbonate ground with no dispersant at a granulometry ofwhich 61% of the particles have a diameter less than one micrometerdetermined by the Micromeritics company Sedigraph 5100 measurement andissuing from a mechanical reconcentration of the centrifugation typefollowing upon this wet grinding at low concentration in terms of drymatter and with no dispersant.

This natural calcium carbonate is a chalk.

The dispersing agents of the different tests of the example are testedwith the same equipment and the same operating method as in the previousexample, with the exception of the dry matter content of the aqueoussuspension of calcium carbonate obtained which is 62% instead of 61%,and the exception of the test 39, where 1.0% by dry weight of dispersingagent is tested.

Test 33

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.15 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 80% acrylic acid and 20% itaconic acid.

Test 34

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.73 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% ethyl acrylate.

Test 35

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.21 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% methacrylic acid.

Test 36

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.42 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% methacrylic acid.

Test 37

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.70 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% methacrylic acid.

Test 38

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.11 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 80% acrylic acid and 20% allylamine.

Test 39

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.10 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 15% acrylic acid, 60% methacrylic acid, 12.5%styrene and 12.5% butyl acrylate.

Test 40

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.54 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 90% acrylic acid and 10% vinyl acetate.

Test 41

This test, which illustrates the invention, uses a copolymer, 100%neutralized with soda, with viscosity index equal to 0.22 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 85% acrylic acid and 15% methyl methacrylate.

All the experimental results are recorded in the following Table 3.

TABLE 3 Brookfield viscosity Brookfield viscosity Viscosity CompositionDose T = 0 T = 8D PRE-AG Tests index (%) (%) 100 rpm (mPa · s) 10 rpm(mPa · s) 33 Invention 0.15 AA 80 ITCA 20 0.4 225 7000 34 Invention 0.73AA 70 EA 30 0.4 960 16000 35 Invention 0.21 AA 70 MAA 30 0.4 1100 1200036 Invention 0.42 AA 70 MAA 30 0.4 850 13500 37 Invention 0.70 AA 70 MAA30 0.4 655 10000 38 Invention 0.11 AA 80 ALLYL 20 0.4 655 10000 39Invention 0.10 AA 15 MAA 60 1.0 800 10000 STY 12.5 40 Invention 0.54 AA90 VAC 10 0.4 600 13000 BUA 12.5 41 Invention 0.22 AA 85 MMA 15 0.4 125015000 AA: Acrylic acid MAA: Methacrylic acid EA: Ethyl acrylate ITCA:Itaconic acid ALLYL: Allylamine STY: Styrene BUA: Butyl acrylate VAC:Vinyl acetate MMA: Methyl methacrylate T = 0 means initial Brookfieldviscosity of the suspension T = 8D PRE-AG means Brookfield viscosityafter 8 days' storage without agitation

The reading of Table 3 allows it to be noted that the copolymers ofacrylic acid having a viscosity index selected from the interval between0.08 and 0.80 make it possible to put into suspension a calciumcarbonate issuing from a mechanical reconcentration of thecentrifugation type following upon a wet grinding at low concentrationin terms of dry matter and with no dispersant, and with granulometrydifferent from that of Example 2.

EXAMPLE 4

This example relates to the proportion of polymer used as a dispersingagent allowing the putting into aqueous suspension of natural calciumcarbonate ground with no dispersant at a granulometry of which 61% ofthe particles have a diameter less than one micrometer determined by theMicromeritics company Sedigraph 5100 measurement and issuing from amechanical reconcentration of the centrifugation type following uponthis wet grinding at low concentration in terms of dry matter and withno dispersant.

This natural calcium carbonate is a marble.

For this test (test 42), the aqueous suspension of marble was preparedby introduction, into the filter cake issuing from the centrifugation,of 2.0% by dry weight, with respect to the dry weight of said filtercake to be put into suspension, of a copolymer 100% neutralized withsoda with viscosity index equal to 0.13 measured according to theaforementioned procedure and composed, in terms of weight percentage, of41% styrene, 15% butyl acrylate, 36% methacrylic acid and 8% acrylicacid, so as to obtain an aqueous suspension of calcium carbonate at aconcentration in terms of dry matter equal to 62%.

After 20 minutes' agitation, a sample of the calcium carbonatesuspension obtained is retrieved in a flask and its Brookfield viscosityis measured by means of an RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 100 rpm with theappropriate spindle.

The following result is obtained: Brookfield viscosity equal to 1550mPa.s.

After a time of 8 days in the flask, the Brookfield viscosity of thesuspension is measured by introduction, into the non-agitated flask, ofthe appropriate spindle of the RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 10 rpm with theappropriate spindle (PRE-AG viscosity=Brookfield viscosity beforeagitation).

The following result is obtained: Brookfield viscosity equal to 3000mPa.s.

EXAMPLE 5

This example relates to the degree of neutralization and the nature ofthe neutralization of the polymer used as a dispersing agent allowingthe putting into aqueous suspension of natural calcium carbonate groundwith no dispersant at a granulometry of which 73% of the particles havea diameter less than one micrometer determined by the Micromeriticscompany Sedigraph 5100 measurement and issuing from a mechanicalreconcentration of the centrifugation type following upon this wetgrinding at low concentration in terms of dry matter and with nodispersant.

This natural calcium carbonate is a marble.

For each test, the aqueous suspension of marble was prepared byintroduction, into the filter cake issuing from the centrifugation, of0.8% by dry weight of dispersing agent to be tested with respect to thedry weight of said filter cake to be put into suspension so as to obtainan aqueous suspension of calcium carbonate at a concentration in termsof dry matter equal to 63%.

After 20 minutes' agitation, a sample of the calcium carbonatesuspension obtained is retrieved in a flask and its Brookfield viscosityis measured by means of an RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 100 rpm with theappropriate spindle.

After a time of 8 days in the flask, the Brookfield viscosity of thesuspension is measured by introduction, into the non-agitated flask, ofthe appropriate spindle of the RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 10 rpm (PRE-AGviscosity=Brookfield viscosity before agitation).

The different homopolymers of acrylic acid tested are:

Test 43

This test, which illustrates the invention, uses a mixed polyacrylate ofcalcium and sodium (15% calcium-85% sodium by mole), the salified withsoda form of which has a viscosity index equal to 0.39 measuredaccording to the aforementioned procedure.

Test 44

This test, which illustrates the invention, uses a mixed polyacrylate ofmagnesium and sodium (15% magnesium—85% sodium by mole), the salifiedwith soda form of which has a viscosity index equal to 0.39 measuredaccording to the aforementioned procedure.

Test 45

This test, which illustrates the invention, uses a polyacrylatepartially neutralized with soda (80% molar) with viscosity index equalto 0.39 measured according to the aforementioned procedure.

Test 46

This test, which illustrates the invention, uses a partially neutralizedmixed polyacrylate of calcium and sodium (15% calcium-65% sodium bymole), the salified with soda form of which has a viscosity index equalto 0.39 measured according to the aforementioned procedure.

Test 47

This test, which illustrates the invention, uses a partially neutralizedmixed polyacrylate of magnesium and sodium (15% magnesium-65% sodium bymole), the salified with soda form of which has a viscosity index equalto 0.39 measured according to the aforementioned procedure.

All the experimental results are recorded in the following Table 4.

TABLE 4 Brookfield viscosity Brookfield viscosity Dose T = 0 T = 8DPRE-AG Tests Neutralization (%) 100 rpm (mPa · s) 10 rpm (mPa · s) 43Invention 85% Na 15% Ca 0.8 840 8000 44 Invention 85% Na 15% Mg 0.8 87010000 45 Invention 80% Na — 0.8 1020 7000 46 Invention 65% Na 15% Ca 0.8920 5000 47 Invention 65% Na 15% Mg 0.8 1550 6000 T = 0 means initialBrookfield viscosity of the suspension T = 8D PRE-AG means Brookfieldviscosity after 8 days' storage without agitation

The reading of Table 4 allows it to be noted that the homopolymers ofacrylic acid having a viscosity index selected from the interval between0.08 and 0.80, whether partially or totally neutralized by at least oneneutralizing agent having a monovalent function and possibly by an agenthaving a polyvalent function, make it possible to put into suspension acalcium carbonate issuing from a mechanical reconcentration of thecentrifugation type following upon a wet grinding at low concentrationin terms of dry matter and with no dispersant.

EXAMPLE 6

This example relates to the nature of the neutralizing agent, having amonovalent function, of the polymer used as a dispersing agent allowingthe putting into aqueous suspension of natural calcium carbonate groundwith no dispersant at a granulometry of which 73% of the particles havea diameter less than one micrometer determined by the Micromeriticscompany Sedigraph 5100 measurement and issuing from a mechanicalreconcentration of the filter press type following upon this wetgrinding at low concentration in terms of dry matter and with nodispersant.

This natural calcium carbonate is a marble.

For each test, the aqueous suspension of marble was prepared byintroduction, into the filter cake issuing from the filtration, of 0.4%by dry weight of dispersing agent to be tested with respect to the dryweight of said filter cake to be put into suspension so as to obtain anaqueous suspension of calcium carbonate at a concentration in terms ofdry matter equal to 63%.

After 20 minutes' agitation, a sample of the calcium carbonatesuspension obtained is retrieved in a flask and its Brookfield viscosityis measured by means of an RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 100 rpm with theappropriate spindle.

After a time of 8 days in the flask, the Brookfield viscosity of thesuspension is measured by introduction, into the non-agitated flask, ofthe appropriate spindle of the RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 10 rpm (PRE-AGviscosity=Brookfield viscosity before agitation).

The different homopolymers of acrylic acid tested are:

Test 48

This test, which illustrates the invention, uses a totally neutralizedpotassium polyacrylate, the salified with soda form of which has aviscosity index equal to 0.39 measured according to the aforementionedprocedure.

Test 49

This test, which illustrates the invention, uses a totally neutralizedlithium polyacrylate, the salified with soda form of which has aviscosity index equal to 0.39 measured according to the aforementionedprocedure.

Test 50

This test, which illustrates the invention, uses a totally neutralizedammonium polyacrylate, the salified with soda form of which has aviscosity index equal to 0.39 measured according to the aforementionedprocedure.

All the experimental results are recorded in the following Table 5.

TABLE 5 Brookfield viscosity Brookfield viscosity Dose T = 0 T = 8DPRE-AG Tests Neutralization (%) 100 rpm (mPa · s) 10 rpm (mPa · s) 48Invention 100% KOH 0.4 130 8000 49 Invention 100% LiOH 0.4 180 3500 50Invention 100% NH₄OH 0.4 120 6000 T = 0 means initial Brookfieldviscosity of the suspension T = 8D PRE-AG means Brookfield viscosityafter 8 days' storage without agitation

The reading of Table 5 allows it to be noted that the homopolymers ofacrylic acid having a viscosity index selected from the interval between0.08 and 0.80 make it possible to put into suspension a calciumcarbonate issuing from a mechanical reconcentration of the filter presstype following upon a wet grinding at low concentration in terms of drymatter and with no dispersant, whatever the nature of the neutralizingagent having a monovalent function.

EXAMPLE 7

This example relates to the use of polymers according to the inventionas dispersing agents allowing the putting into aqueous suspension ofnatural calcium carbonate ground with no dispersant at a granulometry ofwhich 73% of the particles have a diameter less than one micrometerdetermined by the Micromeritics company Sedigraph 5100 measurement andissuing from a thermal reconcentration following upon this wet grindingat low concentration in terms of dry matter and with no dispersant.

This natural calcium carbonate is a marble.

For this test (test 51), the aqueous suspension of marble was preparedby introduction, into the thermally reconcentrated suspension, of 1.0%by dry weight, with respect to the dry weight of said filter cake to beput into suspension, of a totally neutralized sodium polyacrylate withviscosity index equal to 0.39 measured according to the aforementionedprocedure, so as to obtain an aqueous suspension of calcium carbonate ata concentration in terms of dry matter equal to 72%.

After 20 minutes' agitation, a sample of the calcium carbonatesuspension obtained is retrieved in a flask and its Brookfield viscosityis measured by means of an RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 100 rpm with theappropriate spindle.

The following result is obtained: Brookfield viscosity equal to 700mPa.s.

After a time of 8 days in the flask, the Brookfield viscosity of thesuspension is measured by introduction, into the non-agitated flask, ofthe appropriate spindle of the RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 10 rpm with theappropriate spindle (PRE-AG viscosity=Brookfield viscosity beforeagitation).

The following result is obtained: Brookfield viscosity equal to 11,000mPa.s.

This result allows it to be noted that the polymers of acrylic acidhaving a viscosity index selected from the interval between 0.08 and0.80 make it possible to put into suspension, highly concentrated interms of dry matter, a calcium carbonate issuing from a thermalreconcentration following upon a wet grinding at low concentration interms of dry matter and with no dispersant.

EXAMPLE 8

This example relates to the use of polymers according to the inventionas dispersing agents allowing the putting into aqueous suspension ofnatural calcium carbonate ground with no dispersant at a granulometry ofwhich 73% of the particles have a diameter less than one micrometerdetermined by the Micromeritics company Sedigraph 5100 measurement andissuing from a mechanical reconcentration of the centrifugation typefollowed by a thermal reconcentration following upon this wet grindingat low concentration in terms of dry matter and with no dispersant.

This natural calcium carbonate is a marble.

For this test (test 52), the aqueous suspension of marble was preparedby introduction, into the filter cake issuing from the mechanical andthen thermal reconcentration, of 0.8% by dry weight, with respect to thedry weight of said filter cake to be put into suspension, of a copolymertotally neutralized with soda, with viscosity index equal to 0.15 andcomposed of 80% by weight of acrylic acid and 20% by weight of itaconicacid, so as to obtain an aqueous suspension of calcium carbonate at aconcentration in terms of dry matter equal to 72%.

After 20 minutes' agitation, a sample of the calcium carbonatesuspension obtained is retrieved in a flask and its Brookfield viscosityis measured by means of an RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 100 rpm with theappropriate spindle.

The following result is obtained: Brookfield viscosity (100 rpm)=390mPa.s.

After a time of 8 days in the flask, the Brookfield viscosity of thesuspension is measured by introduction, into the non-agitated flask, ofthe appropriate spindle of the RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 10 rpm (PRE-AGviscosity=Brookfield viscosity before agitation).

The following result is obtained: Brookfield viscosity (10 rpm)=4,000mPa.s.

This result allows it to be noted that the acrylic acid/itaconic acidcopolymer having a viscosity index selected from the interval between0.08 and 0.80 makes it possible to put into suspension, highlyconcentrated in terms of dry matter, a calcium carbonate issuing from amechanical and then thermal reconcentration following upon a wetgrinding at low concentration in terms of dry matter and with nodispersant.

EXAMPLE 9

This example relates to the use of aqueous suspensions of mineralfillers as proposed by the invention in the manufacture of coatingcolour for paper.

To this end, the coating colours are prepared by mixing the aqueoussuspensions of mineral fillers to be tested in water with the otherconstituents of the coating colour, the composition by weight of whichis as follows:

100 parts of aqueous suspensions to be tested with a content of 65% indry substance

12 parts of a carboxylated styrene-butadiene latex marketed by DowChemical under the name of DL 905

0.5 part of carboxymethyl cellulose sold by Metsa Serla under the nameof Finnfix 5, the content of dry substance being in the order of 64.5%and the pH being equal to 8.4.

Brookfield viscosity measurements are then taken on the coating coloursprepared in this manner, at ambient temperature and at 20 revolutionsper minute, 50 revolutions per minute and 100 revolutions per minuteusing a Brookfield viscometer of the DVII type fitted with theappropriate spindle.

Test 53

This test, illustrating the invention, uses an aqueous suspension ofcalcium carbonate according to test n°6.

The results of all the experiments are set out in table 6 below.

TABLE 6 Brookfield viscosity in mPa.s. Test n° 20 r/min 50 r/min 100r/min Invention 53 3650 2000 1590

Table 6 shows that an aqueous suspension of calcium carbonate accordingto the invention can be used in the manufacture of coating colour forpaper.

EXAMPLE 10

This example relates to the use of aqueous suspensions of mineralfillers as proposed by the invention in the mass filling for paper. Tothis end, sheets of paper are made from a cellulose pulp of SR 23 degreecontaining a woodless sulphate paste and fibres comprising 80% birch and20% pine. 45 g dry weight of this pulp are then diluted in 10 liters ofwater in the presence of about 15 g dry weight of the filler compositionto be tested to produce experimentally a filler content of 20%. After 15minutes of agitation and adding 0.06% by dry weight, relative to the dryweight of paper, a retention agent of the polyacrylamide type, a sheetis made with a grammage equal to 75 g/m² and filled to 20%. The deviceused to make the sheet is a Rapid-Köthen 20.12 MC modelby Haage.

The sheets prepared in this manner are dried for 400 seconds at 92° C.and in a vacuum of 940 mbar. The filler content is controlled byanalysing the ashes.

The value for opacity of the obtained paper sheet is then determinedusing the DIN 53146 standard.

Test 54

This test, which illustrates the invention, uses the aqueous suspensionof calcium carbonate according to test 6. The value for opacity,measured using the DIN 53146 standard, is 88.

This value shows that anyone of the aqueous suspension of calciumcarbonate, according to the invention, can be used as a mass filling forpaper.

EXAMPLE 11

This example relates to the use of aqueous suspensions of mineralfillers as proposed by the invention in the field of paint and moreparticularly water-based glazed paint. To do that, test 55 according tothe invention is carried out.

For this test, the constituents of the said water-based glazed paintwere added in succession, these being:

40 g of monopropylene glycol 2 g of a biocide, marketed by TROY underthe name of MERGAL ™ K6N 1 g of an anti-foaming agent marketed by HENKELunder the name of NOPCO ™ NDW 217,4 g of the calcium carbonate aqueoussuspension according to test 6 and with a solid content of 65% 200 g ofrutile titanium oxide marked by MILLENNIUM under the name TIONA ™ RL 68450 g of a styrene-acrylic binder in dispersion, marketed by RHODIAunder the name of RHODOPAS ™ DS 910 30 g of butyldiglycol 1 g of Nopco ™NDW 3 g of 28% ammonia 4 g of a thickening agent marketed by COATEXunder the name COATEX BR100P and 49,6 g of water.

After agitating the aqueous composition made up in this way for a fewminutes at a pH equal to 8.5 the Brookfield viscosities of the differentcompositions are measured at 25° C. and at 10 revolutions per minute and100 revolutions per minute using a standard RVT Brookfield viscometerfitted with the requisite spindle.

The Theological stability of the formula over time and in terms oftemperature is determined by measuring the Brookfield viscosities at 10revolutions per minute and at 100 revolutions per minute at 25° C. ofthis same formula after storing at ambient temperature without agitationfor 24 hours and then after storing for one week at ambient temperature.

The rheological stability is also determined by the ICI viscosity whichis a high shear viscosity measured with the use of a plan coneviscometer.

The Stormer KU viscosity is also measured in Krebs Unit with the use ofa Stormer viscometer.

The obtained results of the different measurements are:

At t=0

Brookfield viscosity 10 rpm=4000 mPa.s

Brookfield viscosity 100 rpm=2200 mPa.s

ICI viscosity=160 mPa.s

KU Stormer viscosity=97 KU

At t=24 hours

Brookfield viscosity 10 rpm=8400 mpa.s

Brookfield viscosity 100 rpm=4700 mPa.s

ICI viscosity=130 mpa.s

KU Stormer viscosity=121 KU

At t=8 days

Brookfield viscosity 10 rpm=8200 mPa.s

Brookfield viscosity 100 rpm=4600 mPa.s

ICI viscosity=130 mPa.s

KU Stormer viscosity=121 KU

The reading of these results shows that anyone of the aqueous suspensionof calcium carbonate, according to the invention, can be used in thefield of paint.

What is claimed is:
 1. A dispersing agent for an aqueous suspension ofmineral particles, said dispersing agent comprising a homopolymer ofacrylic acid, a water-soluble copolymer of acrylic acid with one or moreacrylic, vinyl or allylic monomers, or both the homopolymer and thecopolymer, wherein the homopolymer or copolymer has a molecular weightcorresponding to a viscosity index with a value from 0.08 to 0.80, andwherein said mineral particles are derived from mechanicalreconcentration, thermal reconcentration, or both mechanical and thermalreconcentration after wet grinding in the absence of a dispersant at lowconcentrations of dry matter.
 2. The dispersing agent of claim 1,comprising a homopolymer of acrylic acid in a form partially neutralizedor totally neutralized by one or more neutralizing agents having amonovalent function containing an alkaline cation, and optionally by oneor more neutralizing agents having a polyvalent function containing analkaline-earth divalent cation, or a compound containing ahigher-valency cation.
 3. The dispersing agent of claim 1, comprising awater-soluble copolymer of acrylic acid, wherein the one or moreacrylic, vinyl or allylic monomers are chosen from the group consistingof methacrylic acid, itaconic acid, crotonic acid, fumaric acid,isocrotonic, aconitic, mesaconic, sinapic, undecylenic, angelic acid,canellic acid, acrylamido methyl propane sulphonic acid in acid form,acrylamido methyl propane sulphonic acid in partially neutralized form,acrylamide, methacrylamide, esters of acrylic acid, esters ofmethacrylic acids, vinylpyrrolidone, vinylcaprolactame, isobutylene,diisobutylene, vinyl acetate, styrene, alphamethylstyrene, styrenesodium sulphonate, vinylmethylether, allylamine and derivatives thereof.4. The dispersing agent of claim 1, comprising a water-soluble copolymerof acrylic acid, wherein the one or more acrylic, vinyl or allylicmonomers are partially neutralized or totally neutralized by one or moreneutralizing agents having a monovalent function containing an alkalinecation, and optionally by one or more neutralizing agents having apolyvalent function containing an alkaline-earth divalent cation, or acompound containing a higher-valency cation.
 5. The dispersing agent ofclaim 1, wherein the homopolymer, the water-soluble copolymer or both,have a molecular weight corresponding to a viscosity index with a valuefrom 0.20 to 0.60.
 6. A method of preparing an aqueous suspension ofmineral particles, said process comprising mixing the dispersing agentof claim 1 with one or more mineral particles derived from mechanicalreconcentration, thermal reconcentration, or both mechanical and thermalreconcentration after wet grinding in the absence of a dispersant. 7.The method of claim 6, wherein the dispersing agent is mixed in theproportion of 0.1% to 2% by dry weight with respect to the dry weight ofthe mineral particles.
 8. An aqueous suspension comprising mineralparticles, water and 0.1% to 2% by dry weight, with respect to the dryweight of the mineral particles, of the dispersing agent according toclaim 1, wherein said mineral particles are derived from mechanicalreconcentration, thermal reconcentration, or both mechanical and thermalreconcentration, after wet grinding in the absence of a dispersant andat low concentration of dry matter.
 9. The aqueous suspension of mineralparticles according to claim 8, wherein the mineral particles are chosenfrom the group consisting of synthetic calcium carbonates, naturalcalcium carbonates, dolomites and mixtures thereof.
 10. The aqueoussuspension of mineral particles according to claim 8, wherein thesuspension has a concentration, in terms of dry matter, of at least 60%with a Brookfield viscosity less than 2,000 mPa.s measured at 100 rpmimmediately after formation of the suspension and a Brookfield viscosityless than 20,000 mPa.s, measured at 10 rpm after eight days storagewithout agitation.
 11. The dispersing agent of claim 2, wherein thealkaline cation is at least one selected from the group consisting ofsodium, potassium, lithium, ammonium, aliphatic primary amines,aliphatic secondary amines, cyclic primary amines, cyclic secondaryamines, ethanolamines, monoethylamine, diethylamine, andcyclohexylamine.
 12. The dispersing agent of claim 2, wherein thehomopolymer is neutralized by at least one alkaline-earth divalentcation selected from the group consisting of magnesium, calcium, andzinc.
 13. The dispersing agent of claim 2, wherein the homopolymer isneutralized by at least one neutralizing agent having a polyvalentfunction comprising a trivalent cation.
 14. The dispersing agent ofclaim 13, wherein the trivalent cation is aluminum.
 15. The dispersingagent of claim 3, wherein the one or more acrylic, vinyl or allylicmonomers are selected from the group consisting of ethyl acrylate, butylacrylate, methyl methacrylate, phosphate of acrylate of ethylene glycol,phosphate of acrylate of propylene glycol, phosphate of methacrylate ofethylene glycol and phosphate of methacrylate of propylene glycol. 16.The dispersing agent of claim 4, wherein the alkaline cation is at leastone selected from the group consisting of sodium, potassium, lithium,ammonium, aliphatic primary amines, aliphatic secondary amines, cyclicprimary amines, and cyclic secondary amines.
 17. The dispersing agent ofclaim 4, wherein the alkaline cation is at least one selected from thegroup consisting of ethanolamine, monoethylamine, diethylamine, andcyclohexylamine.
 18. The dispersing agent of claim 4, wherein thecopolymer is neutralized by at least one alkaline-earth divalent cationselected from the group consisting of magnesium, calcium, and zinc. 19.The dispersing agent of claim 4, wherein the copolymer is neutralized byat least one neutralizing agent having a polyvalent function that is atrivalent cation.
 20. The dispersing agent of claim 19, wherein thetrivalent cation is aluminum.
 21. The method of claim 7, wherein thecomposition is mixed in the proportion of 0.3% to 1% by dry weight. 22.The aqueous suspension of claim 8, comprising from 0.3% to 1% by weightof the dispersing agent.
 23. The aqueous suspension of claim 9, whereinthe mineral particles comprise a natural calcium carbonate selected fromthe group consisting of chalk, calcite, marble and mixtures thereof. 24.A filler for paper coating or filling comprising the suspension asclaimed in claim
 8. 25. A method comprising coating or mass filling asubstrate or a composition with the aqueous suspension of claim 8,wherein said substrate or composition is a paint, ceramic, drillingfluid, filler for synthetic resin, rubber, detergent, cleaningformulation, cement or plaster.
 26. The dispersing agent of claim 1,comprising an acrylic copolymer comprising one or more polymerized unitsof a monomer selected from the group consisting of an acrylamidosulphonic acid, a phosphate acrylate of ethylene glycol, a phosphateacrylate of propylene glycol, a phosphate methacrylate of ethyleneglycol, and a phosphate methacrylate of propylene glycol.
 27. The methodof claim 6, wherein the dispersing agent comprises an acrylic copolymercomprising one or more polymerized units of a monomer selected from thegroup consisting of an acrylamido sulphonic acid, a phosphate acrylateof ethylene glycol, a phosphate acrylate of propylene glycol, aphosphate methacrylate of ethylene glycol, and a phosphate methacrylateof propylene glycol.
 28. The aqueous suspension of claim 1, wherein thedispersing agent comprises an acrylic copolymer comprising one or morepolymerized units of a monomer selected from the group consisting of anacrylamido sulphonic acid, a phosphate acrylate of ethylene glycol, aphosphate acrylate of propylene glycol, a phosphate methacrylate ofethylene glycol, and a phosphate methacrylate of propylene glycol.